Character mistake: Sherlock says "Cherchez la femme" but pronounces "femme" as "fem" rather than "fam." In earlier episodes, he has been seen speaking fluent French, and so would be unlikely to make so basic an error.

When Holmes and Watson are arguing in the kitchen, Watson puts her mug and phone on the counter. A few times during the scene, the mug switches which side of the phone it's on. The first time it's plausible Watson moves it when off camera, but subsequent to that, we can see enough of Watson to tell she doesn't make enough movements to change the position of the mug.